Fuse



Aug. 23, 1932. E. o. sHWl-:ITZER FUSE Filed April 2, 1927 2 sheets-sheet 1 .Fa/7:07a @5c/711161 @Mimik www @s y Patented Aug. 23, 1932 UNITED STATES EDMUND O. SCHWEITZER, 0F CHICAGO, ILLINOIS FUSE Application tiled April 2, 1927. Serial No. 180,418.

My invention relates to fuses particularly for use on transmission circuits, and the like.

The fuse of my invention partakes of the A fuse is a safety device depending for its' operation upon the ultimate criterion, namely, transformation of the entire electrical energy flowing in the fused circuit into heat. yAlthou h the transformation of electrical energy into heat is essential to the operation of the fuse, it is desirable to convert such flow of energy into heat for as short a time vconnected to the walls of the chamber, prefas possible. A fuse is paradoxical in that it constitutes a standing invitation for ythe electrical energy to'develop into heat, and yet its entire value and function consists in the prevention of further such development of heat. The measure of success of a fuse resides in the certainty with which excessive current ow is converted into heat and the speed with which further heat is then prevented from developing.

The problem of providing a fuse for high tension transmission grows more ditlicult with increases in voltage. Of fuses now on the market the closed liquid quenched type of fuse is, so far as I can find, -the most successful for high tension work. It requires re-filling at the factory. This, from the customers standpoint, is undesirable.

`Accordinfr to my inventionI provide a fuse ofthe liquid quenched typewhich may be refilled in the `field. The theory upon which I have proceeded in the# production of the present fuse isto submerge the fusible element, where the actual release of heat energy occurs, under a maximum head of liquid and to surround the same on all sides with a substantial mass of the quenching liquid.

This mass of quenching liquid supplies by its body the necessary cooling medium for absorbing the heat of the gases formed by the sudden volatilizing of the fuse metal and tends to quench the same. By providing an outlet under a head of liquid only the desired momentary high pressure is secured for b'oth limiting the expansion of the arc and for compelling the desired quick transfer of heat by `contact from the gases to the liquid.

In the preferred embodiment of my invention I provide a substantially spherical chamber of metal `of high tensile strength andi toughness, and disposed the fusible element at substantially the center of thesame. I provide an outlet of the desired size at the upper end of the chamber and dispose a standpipe of insulating material thereabove. This is preferably a glass tube, balelite fiber sleeve, or the like, the chamber and a substantial part of thetube being filled with are quenching liquid. Y

The one terminal of the fusible element is erably directly opposite the opening in line with the standpipe, and the other terminal is yled up through the standpipe to a ferrule, or

the like, upon the upper end of the standpipe.

A spring may be employed for pulling the upper terminal of the fusible element upward in the standpipe if desired. The fuse device will operate withoutthe spring `because the pressure of the gases generated by the eXplosion of the fuse forces the upper fuse terminal and lead out of the standpipe. The` spring may be used to advantage as, on a relatively small over load, the spring may cause ,upward travel of the upper fuse terminal with sufficient rapidity to extinguish the arc before any substantial pressure is generated. Thus the spring operates in conyunction with `the pressure to ldrive the fuse terminal and lead out of the standpipe.- The standpipe is closed at its upper end by aplug or cork to keep out impurities and to retain the liquid.

In order to assist the explosive pressure in expelling the terminal and lead, a loose piston connected to the lead is disposed in the standpipe. This loose piston with the spring and the column of liquid above it forms a means capable of extinguishing a less violent arc by moving the fuse terminal and agitation of the liquid flowing past the loose pis# ton. I am aware that it has heretofore been proposed in the expulsion air fuse to provide a jacket at the point where the fusible element is d'esigned to blow and to depend upon the jacket to assist in expelling the fuse terminal and lead, but the loose piston of my invention is of a different character.

The jacket for the fuse which is here provided consists of a closed air chamber disposed substantially centrally of the pressure chamber. The fusible element lies within said air chamber.

The fuse of my invention, while it is intended to operate primarily as a liquid submerged and quenched type, is capable of operation as a plain expulsion air type of fuse. Therefore, if the liquid should leak out the fuse device is still operative.

Now in order to acquaint those skilled in the art with the manner of constructing and operating a device embodying my invention, I shall describe in connection with the accompanying drawings a specific embodiment of the same.

In the drawings Figure 1 is a longitudinal vertical section through a device embodying my invention;

Fig. 2 is a transverse section taken on the line 2-2 of Fig. 1;

Fig. 3 is a longitudinal vertical section of a modification;

Fig. 4 is a fragmentary view partly in section showing the manner in which the fuse may be re-filled and showing also a. modified form of loose piston;

Fig. 5 is a fragmentary section through the bottom of a modified form of chamber and fuse terminal;

Fig. 6 is a similar fragmentary section through a modified form of upper fuse terminal; and

Fig. 7 is a longitudinal section of a modification of my invention.

Referring now to Fig. 1, I provide a substantially spherical metal chamber 1 which may be made of bronze, steel, Monel metal, or other metal of high tensile strength and toughness capable of sustaining high internal pressure. This chamber 1 is provided with a lining 2 of fused silica, or like insulating material adhering closely to the inner walls of the same. At its upper side a circular fiange or hollow boss 3 is formed integral with the walls of the chamber 1. This hollow boss receives the lower end of a tube 4 which is preferably made of glass, bakelized fiber, or the like, the lower end of which tube is cemented in the hollow boss 3 as indicated at 5. At its upper end the tube 4 carries a metal ferrule 6 upon which is mounted the clamping screw 7.

The ferrule 6 and the hollow boss 3 constitute terminals or ferrules by which the device may be mounted in contact aws or clips for mounting the fuse, preferably 'in vertical or upwardly inclined position.

The fuse may be mounted in horizontal pooccurs.

sition, or in inverted position, since the upper end of the sleeve or tube 4 is closed by a stopper or cork 8 through which extends a terminal or lead wire 9 connected to the terminal screw 7 and thereby to the ferrule 6.

A terminal 10 is mounted at the bottom of the explosion chamber 1, this'constituting a lug or eye secured to the bottom wall of said fuse chamber 1.

The fusible element, in this case a link 11, is connected to the lower terminal 10 and is connected at its upper end to a conductor 12. The conductor 12 is connected to a disc 13 which forms a loose piston in the tube 4. The conductor 12 and piston 13 are in turn connected through a conductor, in this case a spring 14 to the upper lead wire 9 which passes through the cork 8 and is secured to the ferrule 6. The fusible element 11 has its central or active portion 15 disposed within a small air chamber 16, which is formed preferably of moulded bakelite, or the like, to maintain the part of the fusible link which is designed to fuse out of contact with the liquid 17, which fills the chamber 1 and a portion of the tube 4. This chamber 16 is molded in place upon the part of the fuse link which is designed to fuse in order to insure that fusion will occur at a predetermined point. If desired, all of the connection between the terminal 10 and the terminal 9 may be of relatively non-fusible material such as copper, and only that portion within the chamber 16 formed of fusible metal, but I find that this is not` necessary. The liquid in contact with the fuse outside the chamber 16 keeps the same from fusion, and the chamber 16 insures that blowing will occur at the central part of the explosion chamber 1. The walls of the chamber 16 are madeas thin as conveniently possible, since their sole function is to hold a small body of air in contact with the portion of the fuse which is designed first to blow.

The chamber 1 is intended to be filled with tube 4 to a height which will provide sufficient head of liquid to insure the necessary pressure being generated before expulsion If desired. the entire tube 4 up to the stopper 8 may be filled with liquid.

The operation of the device described is as follows. IVhen the parts are in the position shown, the ferrules 3 and 6 form terminals which are mounted in spring jaw Vmounting constituting the terminals ofthe circuit in which the fuse device is connected. The tube 4 is preferably of glass so that the condition of the same may readily be ascertainable by inspection. Upon the occurrence of an over.- load sufficient to fuse the portion 15 within the chamber 16, an arc will be formed in said chamber 16 by the volatilization of the metal forming the fusible. link and an internal pressure will be generated which quickly rupliquid and the liquid is to extend up in the tures the walls of the chamber 16, placing the contents of the chamber 1 under pressure due to such vaporization of the metal. Some of the liquid surrounding the fuse will be volatilized by the heat generated. This will have two distinct and beneficial functions in interrupting the arc. First, the volatilization of the liquid will extract a large amount of heat from the region of the arc thereby cooling the same and hastening deionization of the gases in the region of the arc during the eriod of residual vapor conduction, that is, uring the period immediately following the instant that the current through the arc has passed through its zero value in accordance with the usual sine law. In the second place deionization will be hastened by the production of a region of increased ressure at the arc since the gases resulting ftiom the volatilization of the liquid will necessarily occupy more space than the volume of the liquid from which they are produced, and, it is to be noted, the gases are produced with explosive rapidity. Thereupon, two forces tend to separate the terminals, first, the tension of the spring 14 which tends to draw the upper fuse terminal up through the tube or standpipe 4, and next, the internal pressure in the chamber 1 having release only through the standpipe forces the contents of the standpipe upward, blowing out the cork 8, and expelling the loose piston 13 and connected parts out through the upper end of said tube 4. The result is that even on violent overloads the device quickly interrupts the flow of current. v v

T he device is operative without the filling of liquid, though obviously it is less effective. vhere no liquid is contained in the device the. blowing of the fusible portion415 ruptures the walls of the chamber 16, placing the gases in the chamber 1 under pressure, and permitting the spring 14 to pull the terminal upward. At the same time, the pressure on the loose piston 13 forces the terminal and the spring 14 out through the tube 4, expelling the stopper 8 and the connected parts, operating in general as do air type expulsion fuses, with this distinction, that the chamber is closed due to the sto per 8 and that the outward movement of tlie gases carries the loose piston 13 and positively expels all of the metal parts out of the tube 4.

The fuse may be re-flled in the field by the insertion of another active element, spring, and terminal, and re-filling with liquid and replacing the cork or stopper 8. The manner in which this may be accomplished is illustrated in Fig. 4 where a rod 19 is connected at its lower end to the stud 20 which extends up from the conductor 12. By this means the hook 21 on the lower end of the conductor 1-1 may be secured in the eye 10 and the rod 19 then unthreaded from the stud 20, whereupon the spring 14 is tensioned, the cork or stopper 8 passed over the terminal wire 9 and put 1n place in the upper end of the tube 4, i and said terminal 9 secured under the terminal screw 7.

To facilitate the operation of applying the cork 8, the terminal wire 9 may be made a separate piece as indicated ink Fig. 6, the spring 14 being provided with hook 22 and the terminal wire 9 provided with a hook Q3, so that the operation of renewing or re-filling may be made as convenient as possible.

Also, if desired, the device may be arranged as shown in Fig. 3 to re-fill the same through an opening 24 formed in the bottom wall of the chamber 1. The opening 24 is formed through the bottom wall. the same being reenforced by a flange 25 which is internally threaded so that the entire active element which, in this case, is secured to a plug 26, may be dropped through the opening 24 and into thc tube 4, which forms the standpipe. In this case, the fusible element 15 is a part of the conductor 2T, which is connected at its lower end to the plug 26 and at its upper end to theloose piston 13 and the lower end of the spring 14. y The fusible portion 15 in this case is reduced in diameter within the p air chamber 16 so as to insure blowing at that point.

In Fig. 5 I have shown a construction of the lower end of the conductor 27 for ease in filling. In this case a conical valve seat 30 is formed about an opening in the lower end of the chamber 1, and the lower end of the conductor 27 has a valve 28 connected thereto, this valve having a conical face adapted to contact with the seat 3() and having a squared stem 31 extending loosely through the squared opening 32. The outer end of the stem 31 is threaded, as indicated at 33, and a cap nut 34 draws the valve 28 down against its seat being sealed, at the same time, by a lead washer 35 under the edge'of the cap nut 34. In this way the internal pressure bearing on the valve 28 tends merely to-tighten the same.

' In Fi 4 I have shown the loose piston 36 in the s ape of a hollow cup providing an air space 37 to cushion the initial shock of the explosion, and to permit the liquid in the explosion chamber 1 to begin upward travel without raising the entire column of li uid in the standpipe above it.

qThe relative diameter of the standpipe 4 and of the chamber 1 may be proportioned to secure the'best results. For greater violence of explosion it is desirable to have more rapid out-flow of the liquid and the fuse terminal and connected metal arts and, for this purpose, the diameter of t e tube 4 may be made greater relative to the diameter of the explosion chamber 1. In fact, with the use of the loose piston 13 or 36, as the case may be, the diameter of the standpipe 4 may be made greater without providing too great freedom of discharge and, at the saine time, insuring the removal of all metal parts out of the inside of the device.

In Fig. 7 I have shown a modied form ofthe device in which the fusible link 40 has the portion 41 thereof enclosed in a glass chamber 16 which hermetically seals said portion 41 of the fusible element from contact with the surrounding liquid which fills the surrounding space. In this case the pressure chamber 1 is provided with an opening opposite to the opening in which the standpipe 4 is connected to provide a Well 42 below the chamber 1. This well is formed by a sleeve of insulating material, cemented in a flange 3 similar to the flange 3. The outer end of the sleeve 4 is closed by a cap 43 which is cemented or otherwise secured to the end of the sleeve 4. A tension spring 14 is disposed in said well 42 and, at its outer end, it has the valve member 28 connected thereto, and this valve member is secured upon 'a seat 30 in the cap 43 as disclosed in connection with Fig. 5. A loose piston 44 is mounted on the stem 45 to which the upper end of the spring 14 is connected: This loose piston 44 may be made in the shape of a weight havin passages therethrough to permit liquid to igiow past the same at relatively slow speed, but to ail'ord considerable resistance to rapid flow of liquid therethrough and therearound.

The cap 43 forms one terminal of the device andthe ferrule 6 forms the other terminal, and by these terminals the device is mounted in suitable fuse clips, or the like, on a mounting.

When the fusible portion 41 blows'it shatters the glass seal 16 thereabout, whereupon the liquid which fills the chamber 1 is brought into contact with the arc in the manner previously described in connection with the previous embodiment, tending to quench and restrict the arc so as to extinguish the same. The spring 14 and the force of the explosion in the chamber 1 tends to drive the parts above the fusible portion 41 out of the upper end of the sleeve 4, this being closed loosely by the stopper 8. At the same time, the spring 14'" tends to draw the terminal of the fuse upon which one end of the arc rests down further into the well 42 to agitato the liquid and to bring the arc into contact with fresh liquid which is made turbulent by the action ofthe spring 14.

Thus the lower portion of the device shown in Fig. 7 operates very much in the manner of the Schweitzer and Conrad fuse now on the market in plunging the terminal of the fuse down into a well or path of liquid and spraying liquid upon the arc, if it persists. The upper portion of the device draws the terminal upward and permits the same to be expelled by the pressure generated in said chamber 1.

This form of the device is particularly of utility where relatively high voltages are encountered and where a single long glass sleeve might afford a considerable element of weakness. If desired, a pocket of air such as described in connection with Fig. 4 may be embodied above and/or below the fusible portion 41. 4

This form of the device will operate satisfactorily without liquid, but its effectiveness is decreased. The speed of operation is increased by the separation of the two ends of the spring. The weight 44 serves to assist in lowering the lower terminal of the fuse. The device may be filled from the upper end by releasing the cap nut 34 and the valve 28, whereupon the parts which remain in the device may be removed and a new insert dropped into place and filled with liquid, as described in connection with the previous embodiment.

I do not intend to be limited to the details shown or described.

I claim 1. In a fuse device, an explosion chamber, a standpipe communicating with the explosion chamber, a conductor extending through the \standpipe and chamber and having a fusible portion disposed substantially centrally of the chamber, a jacket for said fusible portion, and a body of liquid in the chamber and standpipe, said jacket comprising a sealed air chamber disposed within said explosion chamber.

2. In a fuse device, an explosion chamber, a tube communicating with said explosion chamber, a conductor extending through said tube and chamber and having a fusible portion disposed substantially centrally of the chamber, a jacket for said fusible portion to confine the heat generated and to insure that fusion will occur at said portion of the conductor, and a loose piston connected to said conductor and disposed in said tube.

3. In a fuse device, an explosion chamber, a closed tube communicating with the upper end of said chamber, a conductor extending through said tube and chamber and having a fusible portion disposed substantially centrally of said chamber, a loose piston connected to said conductor and disposed in said tube, a spring disposed in said tube and connected to the conductor above said fusible portion, and a body of liquid disposed in said chamber and tube.

4. In combination, a sleeve of insulating material, an explosion chamber communicating with the lower end of said sleeve, a conductor extending from the lower end of the chamber through said sleeve and having a terminal at the upper end of said sleeve, said conductor comprising a fusible element, and a separate air chamber sealed from said explosion chamber and embracing said fusible element.

5. In combination, a pressure chamber having a standpipe at its upper end and a well at its lower end, a fusible link disposed substantially centrally ofthe chamber, a spring connected to the lower end ofthe fusible element and being disposed in the well, and a sprin connected to the upper terminal Qf the fusible element and being disposed in the standpipe, said springs pulling in opposite directions and tending to pull the terminals of the fusi' ble element away from each other.

6. In combination, a pressure chamber having a closed well at its lower end and an open standpipe at its upper end, a fuse disposed in the chamber, a spring in the well and a spring in the standpipe tending to separate the terminals of the fuse, said chamber, well and standpipe containing a bath of liquid, and a relatively loose stopper for the upper end of the standpipe.

7. In a device of the class described, the combination of a metal chamber, tubes of insulation communicating at opposite sides of the chamber with the interior of the chamber,

a cap at the outer end of one of the tubes closing said end of the tube, a ferrule on the outer end of the other tube, said cap and ferrule constituting terminals of the device, a fuse device contained in the chamber, and springs connected to the terminals of the fuse device and to the cap and ferrule, respectively.

8. A fuse including a tube of insulation having a closure at one end comprising a. vent cap, a fuse device, and mechanical means responsive to the violent blowing of the fuse for imparting a hammer blow to the cap to insure opening thereof, said means including a spring connected to the fuse device for producing an enlarged gapv in the fuse circuit, anda piston acted upon by the pressure resulting from a violent blowing of the fuse device. 9. A fuse having a chamber of enlarged diameter from which extends a stem of reduced diameter, a fuse device in said chamber, a spring under tension in said stem and connected at one end tothe fuse device for producing an enlarged gap in the fuse circuit upon blowing of the fuse, a bath lof insulating liquid within the chamber and surrounding the fuse device, a piston member connected to said spring and movable in said stem, there being a body of gas above the piston, whereby upon violent blowing of the fuse the increased pressure in the chamber resulting from the vaporization of some of the liquid therein acts upon the piston to accelerate the lengthening of the gap in the fuse circuit. q

10. A fuse including a chamber of enlarged diameter from which extends upwardly a stem of reduced diameter closed at its outer end, a fuse device in said chamber, a spring under tension in said stem and connected at 011e end to the fuse device for producing an enlarged gap in the fuse circuit upon blowing of the fuse, and means for producing a momentar high pressure inthe region of the fuse clrcuit interruption, said means comprising a sealed frangible envelope surrounding the fuse element, and a body of are extinguishing liquid in the chamber and surroundlng the envelope 'whereby upon the initial blowing of the fuse the region of the arc is momentarily maintained at a high pressure due to the inertia of the surrounding liquid, there being a body of gas in the stem, and a cover for the stem comprising an expellable member for relieving the pressure in the chamber upon violent blowing of the fuse device.

In witness whereof,'I hereunto subscribe my name this 30th da of March, 1927.

" EDMUND SCHWEITZER. 

